light blinking objects in cycles render
In the additive RGB color model you create different colors by adding different intensities of the primary colors red, green and blue together.

If you maintain some ratio of red, green and blue but change their values you'll generally end up with darker and lighter shades of the same “color”. The ratio R:G:B = 1:1:1 – i.e. the same value for red, green and blue – is noteworthy as it creates shades of grey.

However, if you also change the ratio of the primary colors then you will end up with different hues.

Let's say you want to create an LED which blinks by cycling from black to some bright orange tone and back to black. For the color orange let's use the RGB ratio of 2:1:0 [1]. This means you need no blue and twice as much red as you have green. If you use sine wave modifiers you have to set amplitude and value offset accordingly.




When the ratio of the primary colors is changed, e.g. by using a different phase offset for each primary color, you'll receive a LED which cycles between different hues.




Edit:
In situations in which you're only interested in single color LEDs, LEDs which cycle between two colors or LEDs which cycle in a set of predefined colors it's worth to consider animating the Emission Strength, the Mix Factor of a MixRGB node and/or the Factor of a ColorRamp node instead of working with three modifiers for the RGB components. This will minimize the work should you later decide to change the color of your LED.



[1] Color values, except for colors entered in the Hex field, are not gamma corrected. Entering an RGB value of 1, 0.5, 0 in Blender will not result in RGB values of 1, 0.5, 0 (or 255, 128, 0) in the final image.